The present invention relates to an airbag mounted, for example, to a steering wheel for a motor vehicle and a folding method thereof.
Airbag arrangements, which are mounted, for example, to bosses of steering wheels for motor vehicles, include an airbag that is inflated by inflow gas in the event of vehicle collision for alleviating an impact to be applied to an occupant or driver. The airbag includes two circular nylon woven cloths, the outer peripheries of which are sewn together to have a shape like a flat bag. The vehicle body-side cloth has a gas introduction port, the periphery of which is fixed to a steering-wheel main body, and from which gas is introduced into the airbag. Normally, the airbag is received, in tiny fold, in the steering-wheel main body, and when an inflator is actuated, it is inflated toward the occupant by gas injected from the inflator so as to hold and restrain the occupant thrown forward, alleviating a collision impact to be applied thereto.
Considering the case where the airbag arrangement is actuated when the occupant is seated in an extremely forward inclined posture to have upper body adjacent to the steering wheel, for example, i.e. out of position, the airbag is demanded to deploy flatly widely to alleviate the pressure applied to the occupant. In response to such demand, JP-A 7-149199 proposes an airbag including a cloth arranged therein for controlling gas flow toward the outer periphery. Specifically, a circular inside cloth is arranged in an outer shell comprising an inflator-side cloth and an occupant-side cloth to conceal a gas introduction port. The outer periphery of the inside cloth is partly sewn to the inflator-side cloth, between which gas is introduced into the airbag.
In the airbag disclosed in JP-A 7-149199, the presence of the inside cloth imposes a positional limitation of a vent hole or exhaust hole. Thus, the vent hole is disposed at the outer periphery of the inside cloth. However, due to an influence of gas exhausted from the vent hole exerted on the occupant, such arrangement of the vent hole may require means for cooling gas supplied from the inflator or an inflator generating relatively low-temperature gas, resulting in difficult reduction in manufacturing cost. Moreover, with outer-periphery arrangement of the vent hole, the vent hole needs to surely face the inflator or the counter-occupant side at deployment of the airbag so as to secure occupant cushioning and pressure regulation, requiring a rather troublesome airbag folding method, resulting in unfavorable deployment characteristics. Further, the inside cloth of smaller than a predetermined length cannot provide operation of changing gas flow, while the inside cloth of larger than a predetermined length will have a center portion greatly expanding to the occupant at gas inflow, raising a problem of the pressure provided to the occupant.
It is, therefore, an object of the present invention to provide an airbag which allows easy enhancement in the deployment characteristics with reduced manufacturing cost. Another object of the present invention is to provide a method of folding such airbag.
The present invention generally provides an airbag mounted to a support member for restraining an object, comprising: a first cloth fixed to the support member, the first cloth being formed with a gas introduction portion; a second cloth superimposed on the first cloth on the side of the object, wherein the first and second cloths have outer periphery joined to each other, wherein the first and second cloths cooperate to define an airbag compartment; a third cloth interposed between the first and second cloths, wherein the third cloth covers the gas introduction portion on the side of the object; a junction which joins the first and third cloths together; a passage defined between the first and third cloths for communication between the gas introduction portion and the outer periphery of the first cloth; an exhaust hole arranged in the junction for communication between the third cloth on the object side and the first cloth on the counter-object side; and a connecting member having one end connected to at least one of the first and third cloths and another end connected to the second cloth.
A main feature of the present invention is to provide such airbag which is prepared by a process comprising: superimposing the first and second cloths on the third cloth; folding the connecting member; and superimposing the folded connecting member on the exhaust hole, wherein the folded connecting member conceals at least part of the exhaust hole.